Head mounted displays (HMDs) and stereoscopic viewing devices (SVDs) have two lenses or apertures that a user can look into to see stereoscopic 3D images. Typically, such systems utilize or generate separate virtual images for the left and right eye. These images are projected toward the user's left and right eyes through separate optics.
People have different distances between their eyes (inter-pupillary distance or IPD). The IPD for adults can range from about 50 millimeters to about 70 millimeters, which is a significant range of variation. To take this variation into account, adjustment of the HMD or SVD is required due to aberrations or stereo separation.
Aberrations include (but are not limited to) Geometric Lens distortion (the lens curves straight lines), transverse/lateral Chromatic Aberration (optics focus different wavelengths of light at different positions on the focal plane), Coma (a variation in magnification away from the center of the optic) and vignetting (image brightness changes from the center of the image). Stereo separation refers to the distance between each virtual image along the axis between two virtual cameras representing the human eyes.
To take these IPD-related effects into account, a HMD or SVD must have optics that can physically adjust to the spacing of the user's eyes or the content being shown on the system needs to be adjusted.
With a HMD/SVD that contains fixed optics (i.e., optics having a stereo separation distance that is fixed mechanically to a specific IPD distance), content will only look correct (e.g., reduced aberrations and correct 3D depth perception) if the user's IPD matches the IPD specified by the system's optical design (a HMD/SVD can be optically designed to deliver correct images to one specific IPD that can be different to the mechanical IPD of optics in the device). Therefore in a fixed optic system, to correctly display high quality images to users with varying IPDs that system must adjust the content that is displayed dynamically.
It is possible to correct the content being shown in software and/or hardware if the user's IPD is known. Hardware (cameras, infrared sensors, etc.) exist to measure the user's IPD, but these can add significant cost, complexity and additional power requirements to a system.
It is within this context that aspects of the present disclosure arise.